I unfortunately do not have such example.
At the moment it would be easier to rely on the legato build system to integrate your application.
So from the yocto point of view, you can do a
legato-af_git.bbappend that defines
SDEF_TO_USE to point to your own sdef.
In recent versions of Legato (> 17.06 I think), you can include the official sdef to append your application, or you can copy the whole sdef and customize it.